Windshield de-icing

ABSTRACT

Apparatus ( 20 ) for cleaning a window ( 24 ) of a vehicle ( 22 ), including a vessel ( 28 ) having an inlet ( 32 ) through which a washing fluid is received from a reservoir and an outlet ( 34 ) through which the fluid is discharged for cleaning the window. There is a heating ( 50 ) for heating the fluid in the vessel, which element preheats the vessel before the washing fluid is received therein, whereby at least an initial quantity of the fluid is rapidly heated and discharged from the vessel.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/101,87 filed on Apr. 8, 2005, which is a continuation of US patentapplication Ser. No. 10/1615,210 filed on Jul. 7, 2003 (now U.S. Pat.No. 6,892,417), which is a divisional of U.S. patent application Ser.No. 09/509,453 filed on Aug. 3, 2000 (now U.S. Pat. No. 6,615,438),which is the US national stage application of International PatentApplication No. PCT/US98/13023 filed on Jun. 24, 1998, and which claimsthe benefit of US Provisional Application Ser. No. 60/076,730 filed onMar. 4, 1998; which is assigned to the assignee of the present patentapplication and incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to fluid heating, andspecifically to heating of a fluid for the purpose of cleaning orde-icing an automobile window.

BACKGROUND OF THE INVENTION

Various methods and devices are known in the art for providing a sprayof heated water or other washing fluid onto the windows of a vehicle.The heated fluid is particularly advantageous in removing ice from thevehicle windshield in cold weather. This ice removal function requiresthat a driver of the vehicle wait while the fluid is heated, before thewindshield can be de-iced. Methods and devices known in the art areimpractical for this purpose, however, since they typically use heat orelectricity generated by the vehicle engine itself to heat the fluid,requiring the driver to wait an unacceptably long time for the fluid toreach a suitable temperature.

Using the vehicle battery to heat the fluid, independent of the vehicleengine, is also problematic because of the large current draw requiredto heat a sufficient quantity of fluid to effectively de-ice thewindshield. The battery cannot typically provide sufficient current toheat the vehicle's entire reservoir of washing fluid in a reasonableamount of time. Although methods and devices have been suggested forheating the fluid on-line, as it is about to be sprayed on thewindshield, the battery also cannot provide enough current to heat aspray of sufficient volume to a high enough temperature to achieveeffective de-icing.

U.S. Pat. No. 5,509,606 describes a hot wash device for an automobilewindshield, which includes a container into which washing fluid from areservoir is pumped and in which the fluid is heated by an electricalheating element before it is sprayed onto the windshield. The containeris insulated and includes a thermostat that is used to ensure that thetemperature of the fluid does not exceed a predetermined maximum. Thecontainer is kept fill, with heat applied as needed to bring the coldfluid pumped into the container up to the desired temperature.

U.S. Pat. No. 5,119,040 describes electric apparatus for washing windowglass of a vehicle. An insulated container is positioned between areservoir of cold washing fluid and spray outlets to the vehicle window,in a position lower than the reservoir so as to be kept fill of fluid.When the vehicle ignition is turned on, an electric heater heats thefluid in the container and remains active while the vehicle is in use.There is no provision, however, for rapid start-up and heating to de-icethe vehicle window.

U.S. Pat. No. 4,090,668 describes a windshield washing and deicingsystem which includes a reservoir having a sealed container therein. Apump transfers washer fluid from the reservoir to the container and fromthe container to a plurality of nozzles. Heated engine coolant is passedthrough a conduit in the reservoir. Electrical resistance wire heats thefluid in the container whenever the temperature drops below a certainminimum. Solenoid valves direct the spray from the tank to the front orrear window of the vehicle, but there is no suggestion of using thevalves for any other fluid control purposes.

U.S. Pat. No. 5,012,977 describes a vehicle window washer in whichwasher fluid in a reservoir is heated, and in which a pump for sprayingthe fluid on the vehicle window has a variable outlet pressure. Thetemperature of the fluid in the reservoir is sensed, and the pump outletpressure is varied accordingly in an inverse manner with temperature ofthe washer fluid, so as to maintain a more consistent fluid deposit onthe window, as the fluid viscosity changes with temperature.

U.S. Pat. No. 5,354,965 describes a system for electrically heating avolume of windshield cleaning fluid in a motor vehicle. A vessel isfilled with the volume of fluid to be heated, using PTC thermistors orother electrical heating elements. A control circuit regulates thelength of time that the fluid is heated, in accordance with a prevailingambient temperature, before the fluid is sprayed on the windshield. Thecircuit also prevents operation of the fluid heating when the vehicleengine is not running.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide improved apparatusand methods for cleaning or de-icing a vehicle window.

It is a further object of some aspects of the present invention toprovide apparatus and methods that enable rapid start-up of de-icing ofa vehicle window.

In preferred embodiments of the present invention, a vessel is providedfor heating a washing fluid before the fluid is discharged toward awindow of a vehicle. Before the fluid is introduced into the vessel thevessel is preheated, preferably by passing an electrical current througha heating element in the vessel for about one minute or less. Whenpreheating is completed, the fluid is allowed into the vessel and israpidly heated by contact therewith, leading to an increase in pressurein the vessel due to vaporization of a portion of the fluid. The fluidis then discharged at a desired temperature and pressure so as to cleanand/or de-ice the window.

Although the preheating of the vessel draws only a moderate electricalinput from the vehicle battery, it enables a sufficient quantity of hotfluid to be generated for de-icing the window before starting thevehicle more rapidly than in any practical window cleaning system knownin the art Moreover, the pressure generated by vaporization of the fluidhelps to clear ice or other blockages that may have formed in tubing ornozzles through which the fluid is sprayed onto the window. It is alsonoted that spraying the heated fluid on the window's exterior surfaceeffectively defogs its interior surface, as well.

In some preferred embodiments of the present invention, after an initialquantity of the fluid has been heated and discharged from the vessel, afurther quantity is introduced into the vessel and immediately heated.Once the further quantity has reached a desired temperature it too isdischarged, preferably after a delay of several seconds. This processcontinues for repeated heat/discharge cycles, until the window has beencompletely cleaned and de-iced. Preferably, the heat/discharge cyclesare timed in a sequence whose parameters, such as discharge duration andintervals between discharges, are varied in accordance with ambienttemperatures of the vehicle and the unheated fluid.

It will be understood that the term “vehicle” as used in the context ofthe present patent application and in the claims can refer to any typeof wheeled vehicle having windows, such as an automobile or truck, aswell as to a boat or airplane. Furthermore, the term “window,” althoughtypically referring to the windshield of a vehicle, can refer to anytransparent surface, including side and rear windows and outer mirrors,as well as covers of headlights and the like. In addition, whenever theterm “cleaning” is used in the present application and in the claims inreference to an action involving spraying heated fluid on a window, theterm will be understood to comprehend de-icing, as well. Those skilledin the art will appreciated that the principles of the present inventionmay be adapted for cleaning and de-icing other surfaces, includinginternal windows and mirrors, for example, as well as for suppliedheated water and fluid for other purposes.

There is therefore provided, in accordance with a preferred embodimentof the present invention, apparatus for cleaning a window of a vehicle,including:

a vessel, having an inlet through which a washing fluid is received froma reservoir and an outlet through which the fluid is discharged forcleaning the window, and

a heating element for heating the fluid in the vessel, which elementpreheats the vessel before the washing fluid is received therein,whereby at least an initial quantity of the fluid is rapidly heated anddischarged from the vessel.

Preferably, the vessel is at least partly drained of fluid held thereinbefore the element preheats the vessel, wherein the vessel includes adrain valve, actuated in cooperation with operation of the heatingelement through which the vessel is at least partly drained. Preferably,the drain valve includes a one-way valve. Further preferably, the fluiddrains into the reservoir, substantially irrespective of the height ofthe reservoir relative to the vessel.

Preferably, the apparatus includes a pump, which conveys the fluid fromthe reservoir to the vessel after the element preheats the vessel,wherein the pump and the reservoir are preferably part of a pre-existingwindow cleaning system in the vehicle, into which the vessel and heatingelement are retrofitted. Alternatively, the entire apparatus may beproduced as an integral unit, including the pump. Preferably, the rapidheating of the initial quantity of the fluid causes the fluid to bedischarged at a pressure substantially higher than a pressure generatedby the pump at the inlet of the vessel.

Preferably, the apparatus includes one or more valves, which regulatepassage of fluid through the vessel responsive to operation of theheating element, wherein the one or more valves open and close incooperation with operation of the heating element. Preferably, the oneor more valves include a solenoid valve or alternatively, a hydraulic,pneumatic or vacuum-operated valve. At least one of the one or morevalves is preferably fixed to the inlet of the vessel or, alternativelyor additionally, to the outlet of the vessel, wherein the at least onevalve fixed to the outlet opens responsive to a pressure increase in thevessel, due to contact between the fluid and the preheated vessel.

In a preferred embodiment, the apparatus includes one or moretemperature sensors, which generate signals responsive to an operatingtemperature of the apparatus, and a controller, which receives thesignals and regulates discharge of the fluid from the vessel responsivethereto. Preferably, after the initial quantity of the fluid isdischarged, one or more additional quantities of fluid are refilled intothe vessel and discharged therefrom intermittently, responsive to thetemperature signals, wherein the quantities are discharged when thetemperature signals indicate that the temperature of the fluid in thevessel is above a predetermined threshold, and the discharge isinterrupted when the temperature of the fluid falls below the threshold.Alternatively or additionally, the quantities are controlled accordingto a predetermined timing sequence, which is selected responsive to thetemperature signals, and the temperature threshold may vary among thequantities in the sequence.

In another preferred embodiment, the controller analyzes the signals todetect a malfunction of the apparatus and interrupts operation of theheating element when the malfunction is detected.

Preferably, at least one of the one or more temperature sensors isinside the vessel. The at least one sensor is preferably substantiallyimmersed in the fluid in the vessel. Alternatively, the at least onesensor is positioned so as to be substantially out of the fluid in thevessel while the heating element preheats the vessel. Preferably,operation of the heating element is interrupted when the temperatureinside the vessel exceeds a predetermined maximum.

In a preferred embodiment, at least one of the one or more temperaturesensors is fixed on an outer surface of the vessel. Additionally oralternatively, at least one of the one or more temperature sensors isfixed to the reservoir or on an outer surface of the vehicle, mostpreferably on an outer surface of the window to be cleaned, covered byan at least partially reflective cover, so as to substantiallyneutralize the effect of solar radiation thereon. Preferably, the fluidin the vessel is heated to a temperature which is varied responsive tothe signals generated by the at least one sensor fixed on the outersurface of the vehicle, or otherwise responsive to a temperature outsidethe vehicle.

Preferably, the vessel includes an inner compartment communicating withthe outlet, in which compartment the heating element is positioned, andan outer compartment, generally surrounding the inner compartment,communicating with the inlet. Preferably, the vessel includes aninsulating outer envelope substantially surrounding the outercompartment and a wall between the inner and outer compartments, whichis preheated by the heating element. Alternatively, the outercompartment is surrounding by one or more additional fluid compartments,external thereto.

Preferably, the apparatus includes a pressure relief valve.

Further preferably, the apparatus includes a bypass line, bypassing thevessel, through which the fluid is conveyed to clean the window withoutheating the fluid, wherein when cleaning of the window is required whilethe element is preheating the vessel, the fluid is diverted through thebypass line. Preferably, an operator of the vehicle selects whether theheating apparatus is to be actuated, such that when the apparatus isde-actuated, fluid is conveyed through the bypass. Further preferably,the apparatus automatically switches between conveying the fluid throughthe vessel and through the bypass, responsive to a heating cycle of thevessel. When fluid is not available from the vessel, unheated fluid is,preferably, automatically conveyed through the bypass line.

In a preferred embodiment, the apparatus includes a remote input device,which is actuated by a user of the vehicle to initiate preheating of thevessel before staring the vehicle.

Preferably, the heating element includes a resistive heating wire.Alternatively or additionally, the heating element conveys heat from aheat source in the vehicle to the fluid in the vessel.

There is also provided, in accordance with a preferred embodiment of thepresent invention, apparatus for cleaning a window of a vehicle,including:

a vessel, having an inlet through which a washing fluid is received froma reservoir and an outlet through which the fluid is discharged forcleaning the window;

a heating element for heating the fluid in the vessel;

a temperature sensor, which senses a temperature in the vessel; and

a valve for controlling flow of the fluid through the vessel, whichintermittently releases quantities of the fluid through the outlet at adesired temperature, responsive to the temperature sensed by the sensor.

Preferably, a windshield wiper is activated intermittently to clean thewindow responsive to the intermittent release of the fluid.

Preferably, the apparatus includes a controller, which regulates theintermittent release of the fluid according to a given timing sequence,preferably a predetermined or programmable sequence, wherein the timingsequence is varied responsive to an ambient temperature in the vehicleor, alternatively or additionally, to a temperature of an outer surfaceof the window.

Preferably, an initial quantity of the fluid is released at asubstantially higher pressure than subsequent quantities.

There is further provided, in accordance with a preferred embodiment ofthe present invention, a method for cleaning a window of a vehicle usinga washing fluid, including:

preheating a vessel;

introducing a quantity of the fluid into the preheated vessel wherebythe temperature and pressure of the fluid are elevated; and

discharging the fluid onto the window at the elevated temperature andpressure.

Preferably, the vessel is drained of fluid before preheating the vessel.

Further preferably, introducing the fluid includes pumping the fluidinto the vessel at a pump pressure, wherein the elevated pressure atwhich the fluid is discharged is substantially greater than the pumppressure.

In a preferred embodiment, the method includes measuring a temperatureof the fluid, wherein discharging the fluid includes controlling thefluid discharge responsive to the temperature measurement. Additionallyor alternatively, a temperature of an outer surface of the vehicle ismeasured, wherein discharging the fluid includes controlling the fluiddischarge responsive to the temperature of the outer surface.

There is moreover provided, in accordance with a preferred embodiment ofthe present invention, a method for cleaning a window of a vehicle usinga washing fluid, including repeating a plurality of times in sequencethe steps of:

heating a quantity of the fluid;

monitoring a temperature of the quantity of the fluid; and

discharging the quantity when a predetermined condition on the heatingof the fluid is satisfied.

Preferably, the predetermined condition is satisfied when thetemperature of the quantity of the fluid reaches a selected level.Alternatively or additionally, the predetermined condition is satisfiedwhen a predetermined period of time has elapsed since beginning theheating.

There is furthermore provided, in accordance with a preferred embodimentof the present invention, vehicle windshield de-icing apparatusincluding: a plurality of individual heating units; and a multi-jacketedhousing wherein each jacket surrounds one of the heating units, thejackets being interconnected by fluid conduits, including an inlet andoutlet port, the housing being connected at the inlet port to awindshield washer fluid source and at the outlet port to a windshieldspray head, the heating units being operated to heat the washer fluidduring flow to the windshield spray head, the heated sprayed fluidproviding a windshield de-icing effect.

There is additionally provided, in accordance with a preferredembodiment of the present invention, an electrically powered windshieldde-icing device for vehicles, including a heatable container forwindshield washing fluid connectable between a washing fluid reservoirand a spray heads opposite the windshield, and provided with an inletport and an outlet port for the fluid, and having an electric heaterelement disposed inside the heatable container, the remaining liquidcapacity of the heatable container not exceeding 300 ml, the heaterelement being connectable to the vehicle battery and being sized to heatthe fluid contained in the heatable container to de-icing temperaturewithin no more than one minute of actuation.

The present invention will be more fully understood from the followingdetailed description of the preferred embodiments thereof, takentogether with the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, pictorial illustration showing apparatus forcleaning a windshield of an automobile with heated washing fluid, inaccordance with a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram showing details of the cleaning apparatusof FIG. 1, in accordance with a preferred embodiment of the presentinvention;

FIG. 3 is a schematic illustration showing a temperature sensor on thewindshield of the automobile of FIG. 1, in accordance with a preferredembodiment of the present invention;

FIG. 4 is a schematic block diagram illustrating the functions of anelectronic controller in the apparatus of FIG. 1, in accordance with apreferred embodiment of the present invention;

FIG. 5 is a the diagram illustrating operation of the apparatus of FIG.1, in accordance with a preferred embodiment of the present invention;

FIG. 6 is a schematic diagram showing details of windshield cleaningapparatus, in accordance with another preferred embodiment of thepresent invention;

FIG. 7 is a sectional view of a heatable vessel for use in windshieldcleaning apparats, in accordance with a preferred embodiment of thepresent invention;

FIG. 8 is a sectional view of a heatable vessel for use in windshieldcleaning apparatus, in accordance with another preferred embodiment ofthe present invention;

FIG. 9 is a perspective view of a heatable vessel for use in windshieldcleaning apparatus, in accordance with still another preferredembodiment of the present invention;

FIG. 10 is an electrical schematic diagram showing the connection ofheating units in the vessel of FIG. 9, in accordance with a preferredembodiment of the present invention;

FIG. 11 is a side view of an internal portion of the vessel of FIG. 10,in accordance with a preferred embodiment of the present invention;

FIG. 12 is a cross-sectional view of the vessel of FIG. 11, taken alongline XII—XII;

FIGS. 13A and 13B are, respectively, top and sectional side views of thevessel of FIG. 11, the sectional view taken along line XIIIB—XIIIB;

FIG. 14 is a schematic pictorial illustration showing window cleaningapparatus in an alternative configuration, in accordance with apreferred embodiment of the present invention;

FIG. 15 is a schematic illustration of a heating vessel for use inwindow cleaning apparatus, in accordance with a preferred embodiment ofthe present invention;

FIG. 16 is a schematic illustration showing a heating wire for use inthe vessel of FIG. 15, in accordance with a preferred embodiment of thepresent invention; and

FIGS. 17A–L are schematic illustrations showing operation of the vesselof FIG. 15 and the apparatus in which the vessel is used, in accordancewith a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1, which is a schematic pictorialillustration showing electrically powered window de-icing and cleaningapparatus 20 for vehicles, in accordance with a preferred embodiment ofthe present invention, shown assembled for use in an automobile 22having a windshield 24 coated with ice 26.

A heatable vessel 28 for windshield washing fluid is connected between awashing fluid reservoir 30 of automobile 22 and spray heads 32, whichspray the fluid onto windshield 24 when actuated by an operator 25 ofthe automobile. The operator may actuate the apparatus either frominside or outside automobile 22, as shown in the figure and describedfurther hereinbelow. Vessel 28 has an inlet port 34, which receiveswasher fluid from reservoir 30, and an outlet port 36 through whichheated fluid is discharged to spray heads 32. The fluid is driven by apump 40, which is generally already present in automobile 22 forspraying unheated fluid to clean windshield 24. A battery 42 providespower to apparatus 20, and wipers 44 clean melted ice and dirt from thewindshield, as is known in the art. A controller 46 regulates theoperation of apparatus 20, and optionally also controls wipers 44 inconjunction with operation of the apparatus. Other aspects and detailsof the apparatus are described further hereinbelow.

FIG. 2 is a schematic, partly sectional diagram showing details ofvessel 28 and other elements of apparatus 20, in accordance with apreferred embodiment of the present invention. Vessel 28 is generallycylindrical in shape and comprises an inner chamber 52 surrounded by anouter chamber 54. Inner chamber 52 is contained and defined by an innerwall 56, preferably comprising a metal such as stainless steel. Outerchamber 54 is surrounded by an outer wall 58 of the vessel, preferablycomprising an insulating material, such as a plastic. A heating element50 inside inner chamber 52 heats the fluid in vessel 28. As a result ofthe concentric arrangement of chambers 52 and 54, heat losses fromvessel 28 are minimized, since heat lost by the hot fluid in chamber 52is used largely to pre-heat the colder fluid in chamber 54. Since thefluid in chamber 54 is cooler, its heat losses through outer wall 58 arerelatively small.

Heating element 50 preferably comprises a resistively-heated electricalelement, which is powered by battery 42 via controller 46, in accordancewith a heating sequence described further hereinbelow. Alternatively oradditionally, element 50 may be heated by exchange of heat with a heatsource in automobile 22, such as the engine cooling fluid or exhaust.Electrical heating by battery 42 is advantageous, however, since itallows vessel 28 to be heated rapidly even before the automobile isstarted. Preferably, element 50 draws approximately 400 W, which typicalautomobile batteries can supply easily. Moreover, vessel 28 ispreferably sized so that within about one minute or less of actuation,it is capable of heating and discharging fluid of a volume andtemperature sufficient to melt ice 26. For this purpose, inner chamber52 preferably contains about 50 ml of the fluid. It will be appreciated,however, that the principles of the present invention may similarly beapplied by scaling the volume of vessel 28 and the power of element 50to any required capacity. In particular, when apparatus 20 is used inlarger vehicles, such as trucks or boats, the volume and power draw ofthe vessel will typically be substantially larger than in automobile 22.

When operator 25 of vehicle 22 actuates apparatus 20, controller 46allows current from battery 42 to flow in heating element 50, so thatvessel 28 begins to heat up. Any fluid in the vessel is preferablyallowed to drain out through a drain port 60, by opening a drain valve62. Valve 62, like other valves used in apparatus 20, as will bedescribed hereinbelow, preferably comprises a solenoid valve, of anysuitable type known in the art, which is controlled by controller 46.The controller preferably applies a relatively high initial current toopen the valve, but then reduces the current to a lower level to holdthe valve open Thus, element 50 pre-heats the vessel, includingparticularly inner wall 56. The heat that builds up in the vessel tendsto vaporize fluid remaining therein, generating pressure that forces thefluid out through port 60, regardless of whether vessel 28 is positionedhigher or lower than reservoir 30. Preferably, a temperature sensor 64measures the temperature in vessel 28 and provides feedback tocontroller 46.

After the vessel has reached a desired temperature, preferably withheating element 50 reaching a temperature of several hundred degreescentigrade drain valve 62 is closed and an inlet valve 66 is opened.Alternatively, the valves may simply be opened after a predeterminedtime has elapsed, since the presence of a residual amount of fluid atthe bottom of vessel 28 will effectively prevent severe overheating ofthe vessel. Pump 40 is operated to convey an initial quantity of washingfluid, preferably between 30 and 50 ml, from reservoir 30 to inlet port34. A one-way valve 68 preferably prevents back-flow of the fluid towarddrain port 60. An outlet valve 74 is preferably a three-way valve, i.e.,of a type having two inlets and a single outlet (in which fluid may alsoenter through the outlet and flow back to the inlets), enabling eitherof the inlets to be in communication with the outlet. Valve 74 is set toallow flow from outlet port 36 to spray heads 32, and to block flowthrough a bypass line 76. Alternatively, separate valves may be providedfor the outlet and bypass line.

The fluid fills outer chamber 54 and flows into inner chamber 52 throughopenings 70 in inner wall 56. An additional opening 72 near the top ofwall 56 aids in pressure equalization between the inner and outerchambers. Upon contact with the hot element 50 and wall 56, the fluid israpidly heated, causing a portion of the fluid to vaporize. The pressureof the vaporization forces the hot fluid out through outlet port 36 andspray heads 32, at an elevated temperature and pressure. Optionallyoutlet valve 74 is held closed even after opening inlet valve 66, and isopened only after sufficient pressure has built up in vessel 28, eitherautonomously or operated by controller 46. The hot, pressurized fluidnot only facilitates rapid melting of ice 26 on windshield 24, but alsois capable of blowing out blockages in fluid lines between outlet port36 and spray heads 32 that may be caused by ice or dirt. Preferably, aone-way valve 78 shunts outlet port 36 to ambient air so as to relievevacuum conditions that may arise.

After the initial quantity of heated fluid has been discharged, pump 40and inlet valve 66 are operated to refill vessel 28. Although heatingelement 50 and wall 56 are no longer as hot as they were before theinitial quantity of the fluid was introduced into the vessel, they stillretain some residual heat, facilitating rapid heating of the refilledfluid. When the refilled fluid reaches a desired temperature and/orafter a predetermined period of time, it is discharged through valve 74and spray heads 32. This process is repeated a desired number of timesin sequence, until an entire sequence of discharges has been completed,as described hereinbelow, or until the windshield has been cleanedand/or de-iced, or until the temperature in vessel 28 drops below apredetermined minimum, or until it is interrupted by operator 25. (It isnoted that under normal conditions, the temperature of the vessel willgenerally decrease from one quantity to the next in the sequence. Ifcontroller 46 receives an indication of an increase in the temperature,such an increase will generally be indicative of a malfunction, forexample, a failure of fluid to refill the vessel, and the controllerwill preferably interrupt the power supplied to element 50.) The drivermay then again actuate apparatus 20 and begin a new cycle of heating andfluid discharge.

Preferably, each time vessel 28 is refilled, heated fluid is dischargedthrough the spray heads for about 3 sec, at intervals of about 5 sec orlonger between fills, generally as determined by the time needed for thefluid to reach a desired temperature. The temperature of laterdischarges in the sequence may be less than that of the initial andother earlier discharges. Further preferably, wipers 44 are operated incooperation with the discharge of fluid from apparatus 20, so that thewipers go on only during and shortly after the fluid discharge.Optionally, wiper operation may be delayed, so that the wipers do notoperate during the initial discharge, when ice 26 has not yet melted,but only start from the second and subsequent discharges.

After the sequence of discharges of heated fluid is completed, valves 66and 74 are closed (relative to vessel 28), and drain valve 62 ispreferably opened, so that any fluid remaining in the vessel can drainback into reservoir 30. (Pump 40 is generally not sealed againstback-flow.) An upper end 61 of drain port 60 is preferably elevatedrelative to the bottom of chamber 52, so that a minimal amount of fluidwill be left in vessel 28 even after draining. The vessel is then readyfor rapid operation the next time apparatus 20 is actuated.

Bypass line 76 allows unheated fluid from reservoir 30 to be pumpeddirectly to spray heads 32, without passing through vessel 28. Line 76is open to the spray heads whenever valve 74, which is preferably athree-way valve, as noted above, is closed relative to outlet port 36.Line 76 can be used in warm weather, when de-icing is not needed, orwhen a cleaning spray is needed immediately, and there is not time toheat the fluid. Preferably, valve 74 remains open relative to line 76,so that fluid from the line is conveyed to spray heads 32, whenever theheating apparatus is not actuated. A one-way valve 80 in line 76preferably blocks any back-flow of fluid through the line.

Apparatus 20 thus provides additional window-cleaning functionality forautomobile 22, at relatively low cost and without interfering withpre-existing window washing capabilities. The apparatus may either beinstalled as part of the window washing system in a new automobile, orit may easily be retrofitted into an existing washing system. Althoughthe parts of apparatus 20 are shown in FIGS. 1 and 2 as being in certainpositions and orientations relative to automobile 22 and the washingsystem therein, other positions and orientations are clearly possible.For example, vessel 28 may be placed at a different angle from theorientation shown in the figures, as long as ports 34, 36 and 60 aresuitably positioned and oriented in the vessel.

Although in the preferred embodiment shown in FIG. 2, apparatus 20includes valves 62, 66 and 74 controlling ports 60, 34 and 36 of vessel28 in a certain fluid flow configuration, it will be understood thatother configurations may also be used. In particular, it is notnecessary to use all three valves. For example, valves 66 and 74 may bedispensed with, along with line 76, and pump 40 used to drive andcontrol the fluid flow through vessel 28. Furthermore, although theparts of apparatus 20 are shown, for the sake of clarity, as separateunits connected by tubing, in actuality at least a portion of theapparatus is preferably constructed as a block, to minimize heat losses.Furthermore, in such a configuration, cold washing fluid can be made topass near the solenoid valves, removing the heat therefrom andincreasing the efficiency of the fluid heating process. It will beappreciated that in any case, because apparatus 20 is largely closed andoperates in a series of short heat/fill/discharge cycles, any leakage orfluid loss will generally have only a minimal effect on its operation.

Control of apparatus 20 by controller 46 is described hereinabove asbeing based on feedback to the controller provided by sensor 64. Thissensor is shown in FIG. 2 as being placed at the upper end of vessel 28,where it will measure the temperature either of vapor or fluid inchamber 52, depending on whether the chamber is empty or filled.Controller 46 preferably tracks and monitors changes in temperaturesensed by sensor 64 during heat/fill/discharge cycles of vessel 28. Ifthe temperature exceeds a predetermined maximum, or if temperaturechanges do not follow a predetermined normal profile, the controllerwill conclude that a malfunction has occurred, such as blockage of inlet34 or outlet 36 or a failure of sensor 64, and will preferably interruptoperation of the apparatus and notify operator 25 by an appropriatesignal.

In addition or alternative to sensor 64, there may be a temperaturesensor nearer the bottom of the vessel, to measure the fluid temperaturetherein. Other sensors, such as a pressure sensor or pressure-stat or afluid level sensor, may also be fixed in the vessel and provide feedbackto controller 46. Further temperature sensors may also be used,including a sensor 82 on an outer surface of vessel 28, a sensor 84 inreservoir 30 for measuring the temperature of fluid therein, and asensor 86 on an outer surface of automobile 22, most preferably onwindshield 24. These sensors provide inputs to controller 46, whichaccordingly sets parameters such as the voltage applied to element 50and/or the lengths of time for which the element and fluid in vessel 28are heated.

Preferably, the controller sets the parameters so that the fluid issprayed onto windshield 24 at a temperature high enough to melt ice 26quickly under prevalent ambient conditions, as indicated by sensor 86,for example, but not so high (relative to the temperature of thewindshield) as to create a danger of cracking the windshield orviolating safety regulations in this regard. The selection of theparameters is preferably automatic, without requiring intervention byoperator 25 of automobile 22, except to actuate or de-actuate apparatus20 as desired.

FIG. 3 is a schematic illustration showing positioning of temperaturesensor 86 on windshield 24, in accordance with a preferred embodiment ofthe present invention. In order for controller 46 to determineaccurately to what temperature the fluid should be heated, it isnecessary to know the temperature of the outer surface of windshield 24.If sensor 86 is placed openly on the windshield and exposed to the sun,however, it will typically read a higher temperature than that of thetransparent windshield itself. Therefore, sensor 86 is preferablycovered by a reflective cover 88, thus largely neutralizing the effectof solar radiation on the temperature reading.

When operator 25 is in automobile 22, he or she actuates apparatus 20either by means of a switch on the dashboard or by signaling controller46 using an existing wash/wipe switch already present in the automobile.For example, the operator may press or pull the existing switch two orthree times in rapid succession to turn apparatus 20 on or off.

In addition, as illustrated in FIG. 1, operator 25 may use an optionalremote control 90 to actuate apparatus 20 before getting into automobile22. Remote control 90 may also be used to initiate automatic operationof wipers 44, and thus to clean and de-ice windshield 24. The remotecontrol may be of any suitable type known in the art, including eitheran active device, such as a RF transmitter, or a passive device, such asan optical or infrared retroreflector. By actuating the apparatus beforegetting into the automobile, the operator can reduce the length of timespent waiting for the fluid to heat up.

FIG. 4 is a schematic block diagram illustrating the operation ofcontroller 46 in apparatus 20, in accordance with a preferred embodimentof the present invention Controller 46 is preferably coupled to anantenna 92, for receiving signals from remote control 90. As describedhereinabove, the controller receives signals from temperature sensor 64,as well as other sensors, such as sensor 84. It also receives electricalpower from battery 42 and distributes the power, preferably by means ofrelays (not shown), to valves 62, 66 and 74 and to pump 40 and heatingelement 50.

Antenna 92 can also be used to allow wireless control of apparatus 20when operator 25 is inside the car, so that there is no need to connectadditional wires and switches on the dashboard of automobile 22.Alternatively, controller 46 may be connected by wire to an operatingswitch and indicator lamp (not shown in the figures), by means of whichthe operator actuates apparatus 20 and is notified of its properoperation or, possibly, malfunction.

Before providing power to the valves, pump and heating element,controller 46 preferably performs a self-test. The test includesmeasurement of input voltage from battery 42 (which must preferably beat least 9 volts for a typical automobile 22 having a 12-volt battery),as well as checking that the electrical resistance of heating element 50is within predetermined bounds. If any part of the self-test fails,controller 46 will not allow apparatus 20 to operate, and willpreferably provide a malfunction indication to operator 25.

FIG. 5 is a timing diagram illustrating a sequence 96 ofheat/fill/discharge cycles of apparatus 20, in accordance with apreferred embodiment of the present invention. Initially, as describedhereinabove, drain valve 62 is opened and heating element 50 isenergized to pre-heat vessel 28. Valve 62 is closed, preferably afterabout 15 sec. Alternatively, the drain valve may be held closed for ashort period, preferably about 20 sec, so that the fluid in vessel 28 isheated to a high temperature before the valve is opened. Thisalternative is particularly useful if controller 46 determines that oneof the valves, particularly inlet valve 66, is stuck and will not open,in which case the heated fluid is used to force the valve open.

Heating continues until sensor 64 reaches a target temperature,preferably about 85° C. (dependent on the exact position of the sensor),in chamber 52, or for about 70 sec, if the temperature does not reachthe target temperature. At that point, pump 40 and inlet and outletvalves 66 and 74 open, to admit and discharge the initial quantity offluid. The temperature In chamber 52 drops, and is subsequentlyreheated, preferably to about 60° C., whereupon a second quantity of thefluid is admitted and discharged. The process of reheating, fill anddischarge continues for a predetermined number of cycles, or untilterminated by operator 25.

After the final discharge in sequence 96, drain valve 62 is opened, andheating element 50, which is energized substantially continuouslythroughout the sequence, remains energized for about 15 sec more, inorder to heat and drive out of vessel 28 as much as possible of anyfluid remaining therein, down to the level of upper end 61. Theapparatus is then ready to begin the next sequence, when required by theuser.

FIG. 6 is a schematic illustration showing an alternative configurationof apparatus 20, in accordance with a preferred embodiment of thepresent invention. Except as indicated hereinbelow, the parts of theapparatus shown in FIG. 6 are substantially similar or identical tothose shown in FIG. 2 and described with reference thereto. Thisembodiment differs from that of FIG. 2 in that in FIG. 6, outlet valve74 is eliminated, and inlet valve 66 is a three-way valve, as describedhereinabove, which alternately connects inlet port 34 or bypass line 16to pump 40. Instead of outlet valve 74, a one-way valve 98, preferably aspring-loaded one-way valve, prevents fluid passing through bypass line76 from flowing back through outlet 36 into vessel 28 when valve 66 isopen in the direction of the bypass line. On the other hand, when valve66 is open in the direction of inlet port 34, the resultant pressure invessel 28 forces valve 98 open, so that heated fluid is dischargedthrough spray heads 32.

Referring now to FIG. 7, there is seen in a sectional view a heatablevessel 128 for use in apparatus 20, in accordance with an alternativeembodiment of the present invention. Although the structure of vessel128 is somewhat different from that of vessel 28, it may be used in asubstantially similar manner. Outlet port 34 may in this case also beused as a drain port.

FIG. 8 illustrates another heatable vessel 130 of cylindrical form, inaccordance with a preferred embodiment of the present invention.Advantageously vessel 130 has an outer enclosure 132 made of a rigidplastic tube, forming one of two spaced-apart walls. An inner wall 134comprises a plastic tube 136 inside a metal tube 138. Metal tube 138 ispreferably made of stainless steel which, being a poor heat conductoramong metals, reduces heat losses. Plastic tubes 132 and 136 are made ofa material which has a wide temperature operating range, for examplepolyetheretherketone or polyphenylene sulfide. Using a pair of end-caps140 and 142 which are epoxy filled, tubes 132, 136 and 138 are easilyheld in alignment. The embodiment shown is particularly useful formanufacturing moderate quantities without incurring high tooling costs.

Inlet port 34 and outlet port 36 comprise nipples for the respectiveattachment of the ends of plastic tubes (seen generally in FIGS. 1 and2) used for connecting between washing fluid reservoir 30 and sprayheads 32, which is preferably divided by cutting during installation ofapparatus 20. Drain port 60 allows fluid to return to reservoir 30 afterthe apparatus has been used, as described hereinabove.

In the embodiment shown in FIG. 8, heating element 50 is a combinationof three electric resistance elements, which are connected in parallel.A single burnt-out element will thus allow the device to continue tofunction, though at reduced power.

Referring now to FIG. 9, there is shown a perspective view of anotherheatable vessel 150 for use in apparatus 20, in accordance with apreferred embodiment of the present invention. A terminal 152 isconnected internally to a set of heating units (shown in FIG. 11), eachhaving an outer jacket through which the washer fluid passes. Thenegative, or ground connection of vessel 150 is made directly to thebody of the heating units mounted therein, via a bridge connector 154and a retaining band (not shown) which secures vessel 150 to automobile22. Insulation material 156 provides the vessel with thermal insulation,typically by a lightweight, low conductivity material.

As will be further described with reference to the figures that follow,vessel 150 includes three separate, individual heating units, eachlocated in a housing jacket through which fluid flows from washer fluidreservoir 30 to windshield spray heads 32. By a novel arrangement of theheating units and fluid jackets, the fluid is pre-heated during flow andis re-circulated to obtain the maximum effective temperature whenexiting as a jet from the spray heads. The heating units are electricaland designed to provide sufficient heat capacity such that during fluidflow in the system, a sufficient temperature is immediately reached.Thus, the inventive design is effective in providing a washer fluidsystem for de-icing of windshield 24, without requiring a long delay aswith prior art systems based on vehicle engine heat. Unlike prior artsystems, no pre-heating of the washer fluid is required, and thecapacity of immediate hot washer fluid is limited only by the size ofthe fluid reservoir. The inventive unit uses the existing washertechnology, hoses and power source. Because vessel 150 is designed toprovide a substantially continuous flow of fluid, which is heated duringflow, it will typically be capable of providing a slower flow of hotfluid onto windshield 24 than the high flow rate of the bursts of hotfluid from vessel 28.

Referring now to FIG. 10, there is shown an electrical schematic diagramof the heating units' connection in vessel 150. A single 100 wattheating unit 166 is connected in parallel with two 150 watt units 162and 164, providing a 400 W total configuration. This heating capacityachieves nearly instant heating of the washer fluid. In this fashion,there is no significant time delay from windshield washer systemoperation until exit of hot spray. This is because the heating isachieved during fluid flow in the system, without changing the systemflow rate and pressure. Optionally, only one or two of units 162, 164and 166 may be used when a relatively lower temperature, and thereforeless heating power, is required.

In operation, when electrical switch 168 is closed, vessel 150 operatesimmediately to heat the washer fluid in the system such that a hot fluidjet spray exits spray heads 32 and begins to clean windshield 24 vianormal operation of wipers 44. Since the heating need not be continuous,electrical switch 168 can be an intermittent type, to periodicallyinterrupt current. A corrosion-resistant type of electrical switch istypically used.

Other than pressing switch 168 closed, operator 25 need not do anythingfurther, as the system operates by spraying washer fluid atapproximately 50 degrees above the ambient temperature (or at anotherappropriate temperature, in accordance with operating conditions), andtogether with the wiper motion, the fluid melts and cleans thewindshield of ice. Within an interval of only about 15 seconds, thewindshield is normally cleaned and de-iced, and driving can begin.Re-freezing of liquid is very unlikely in this very short period.

Referring now to FIGS. 11 and 12, there are shown, respectively, a sideview and a sectional view of the internal portion of vessel 150, inaccordance with a preferred embodiment of the present invention. Vessel150 contains a set of three heating units 232, 234 and 236. Each ofheating units 232–236 is typically provided as a resistance load heater,as shown in the schematic diagram of FIG. 10. Individual outer jackets238, 239 and 240 are constructed around each of heating units 232–236 sothat each surrounds its own internal seating element, to enable washerfluid to quickly absorb heat during flow in the outer jackets 238–240.

As stated above, the heating us are designed for 12-volt operation andare provided as sealed, corrosion-resistant units. Alternatively, theunits may be designed to operate at 24 volts, or any other suitable DCor AC voltage. Their dimensions are so as to define an annular flowpassage (see FIG. 13A) between each unit and its outer jacket, ofdimensions which enable maintenance of the desired system fluidpressure, as set by the vehicle manufacturer.

Fluid inlet pipe 34 is constructed so as to extend alongside the entirelength of heating units 232–236, and is connected to outer jacket 239 ofheating unit 234 at its lower end 244. This construction provides apre-heating function, such that the washer fluid flowing in pipe 34absorbs heat energy emitted by heating units 232–236 before enteringouter jacket 239.

The flow of washer fluid through jacket 239 causes it to be heated byheating unit 234, by absorbing heat from the heating element. Once thewasher fluid has reached the top of jacket 239, it flows via aconnecting tube 246 and re-enters vessel 150 at the lower end of outerjacket 240, so as to be heated during flow therethrough by heating unit236. Upon reaching the top of jacket 240, the washer fluid is againdirected via a connecting tube 248 so as to re-enter vessel 150 at thelower end of outer jacket 238.

At the top of outer jacket 238, there is connected fluid outlet pipe 36,through which the washer fluid exits vessel 150 after flowing throughouter jacket 238 and being heated by heating unit 232. Thus, after thepassage through outer jackets 238–240, the washer fluid is provided withthe maximum possible heat level before flowing to spray heads 32 mountedopposite windshield 24. Spray heads 32 may be specially-designed with anadjustable angle to direct the spray at the most effective point on thewindshield.

In FIG. 12, a cross-sectional view of vessel 150 is shown, taken alongsection lines XII—XII in FIG. 11, revealing further construction detailsof heating units 232–236 and outer jackets 238–240. Fluid inlet pipe 34and the arrangement of connecting tubes 246 and 248 is also shown. Thedesign of heating units 232–236 and outer jackets 238–240 in closeproximity to each other adds to the heat efficiency of the design of thevessel.

Heat efficiency design considerations also affect the choice ofmaterials to be used in vessel 150. For example, choice of copper orbrass tubing for inlet tube 34 insures high heat conductivity, whiletubes 246, 248 and 36 should be chosen of low thermal conductivitymaterial, to ensure minimum heat loss. Tubes 34 and 36 have toothed endportions for easy connection thereto. Outer jackets 238–240 are alsomade from materials chosen for heat efficiency considerations, to havelow thermal conductivity.

In FIGS. 13A–B, there are shown, respectively, a top view and asectional side view of vessel 150, wherein the sectional view is takenalong section lines XIIIB—XIIIB. The construction of outer jackets238–240 is shown in detail including annular flow passage 249 definedaround each of heating units 232–236, and a collection chamber 252defined at the lower end of vessel 150.

Based on the above description, the design of vessel 150 typicallyfeatures a stainless steel construction of approximately 200 mm length,with each outer jacket having overall diameter of 12–13 mm, and wallthickness of 1 mm. Heating units 232–236 are typically each 8 mm indiameter. The overall diameter of the vessel is approximately 51 mm.Fluid inlet pipe 34 and outlet pipe 36 are typically constructed of 3/16inch diameter pipe. This design assures that vessel 150 is a compact,heat efficient unit which does not limit flow rates or pressures. Aswill be understood by those skilled in the art, various of thedimensions can be designed in accordance with existing washer systemdesigns or particular vehicle manufacturers, to maintain the nominalflow rate and pressure of the fluid flow.

As will be appreciated by those skilled in the art, the heating ofwasher fluid during its flow through the system is the main advantage ofvessel 150, since the heating occurs while the fluid is moving, and notwhile standing. The particular flow rates and design dimensions can beeasily established in accordance with design techniques familiar tothose skilled in the art. In addition, the choice of heating unitcapacities may be increased for particular vehicles, such as trucks andbuses.

Referring now to FIG. 14, there is shown an alternative installationapproach for window cleaning apparatus 220, including vessel 150, inwhich the spray heads 32 are located on windshield wipers 44 themselves,in accordance with a preferred embodiment of the present invention. Inthis arrangement, spray heads 32 are connected via flexible tubes255–256, each of which is secured within a slot 258 provided on theunderside of wipers 44. Thus, hot spray is delivered directly to thewindshield at the location at which the greatest de-icing effect isobtained, since the wipers 44 physically break the ice. It will beunderstood that wipers 44 must be operated while the fluid is beingsprayed from spray heads 32.

In summary, apparatus 220 of the present invention can be provided as alow-cost, easily manufactured accessory for existing windshieldwasher/wiper systems or it can be provided in new vehicle designs. Therugged and simple design of vessel 150 makes it an attractive add-onaccessory, which provides an effective and quick solution to windshieldicing problems, enhancing comfort and safety. Apparatus 220, in additionto being simple and easily installed, does not complicate the vehiclemanufacturer's new car assembly line, nor does it burden existing washersystems to which it is applied, in a five-minute installation process. Amanual user control existing in the vehicle is preferably used tooperate the wiper fluid pump.

FIG. 15 schematically illustrates a vessel 300, for use with apparatus20 or 220, mutatis mutandis, in accordance with another preferredembodiment of the present invention. In vessel 300, a single jacket 312is used to hold three separate heating elements, one of which, anelement 304, is shown in the figure extending longitudinally through thevessel. Jacket 312 preferably comprises steel or other materialgenerally cylindrical in shape and having two opposed ends. At one end,there is a cap 320 defining a chamber 322, having a volume preferablybetween 24 and 40 ml, depending on the size of the vehicle in which itis installed. Inlet port 34 and outlet port 36 provide communicationinto the chamber, although as will be described hereinbelow, at certaintimes washing fluid may flow in through the outlet and out through theinlet port.

FIG. 16 is a schematic, sectional illustration of a wire 310 from whichelement 304 is wound, in accordance with a preferred embodiment of thepresent invention. Wire 310 is substantially circular in cross section,and is formed of a magnesium oxide core 306 surrounded by a ceramicsleeve or coating 308. Preferably, the core has a diameter in the rangeof 0.07–0.14 mm. For example, for standard cars, a 500 W unit issufficient, and wire 310 may have a 0.07 mm core. For larger vehicles,such as trucks, a 0.14 mm core may be necessary to generate up to 700 Wof heat. Sleeve or coating 308 is preferably deposited by a standardlaser process using a high-density ceramic powder, as is known in theart. Preferably, coating 308 has a thickness of about 0.10 mm

The two ends 314 of element 304 are provided with magnesium oxideconnectors, which are coupled to be powered via controller 46 asdescribed hereinabove. In this embodiment, controller 46 preferablysenses whether the motor of automobile 22 is operating, for example bydetecting an AC ripple on the voltage from battery 42, and does notallow power to be provided to vessel 300 unless the motor is running, soas to avoid discharging the battery.

Cap 320 is filled with an epoxy or other material capable ofwithstanding high temperatures up to 700° C. In a preferred embodiment,controller 46 is contained in the cap, as shown in FIG. 15. In addition,ports 34 and 36 are provided with valves 366 and 374. These valves arepreferably made of a silicone rubber and are capable of operating athigh temperatures such as 700° C. The valves are coupled to controller46 by wires (not shown in the figure) to indicate the positions of thevalves and to control their operation. Valves of this kind are availablefrom U.S. Plastics of Lima, Ohio.

FIGS. 17A–L are schematic diagrams showing states of vessel 300 andvalves 366 and 374 illustrative of the operation of the vessel, inaccordance with a preferred embodiment of the present invention. Priorto operation, chamber 322 in vessel 300 is empty, and the valves areopen. Operator 25 gets in automobile 22, starts the engine and, in orderto de-ice windshield 24, operates pump 40. The pump generates a pressureat inlet port 34. The pressure is sensed by valve 366, whichautomatically closes without any command from controller 46. Thisposition is shown in FIG. 17A

Next, valve 366 wakes up controller 46 to initiate a de-icing process.The first step of this process is to heat up element 304 by connectingbattery 42 across element 304. In the absence of water in chamber 322,the chamber heats quickly to a very high temperature. The temperature ofthe chamber is monitored by a sensor, such as sensor 64, in the chamber.When the sensor reaches a preset level, preferably about 600° C.,controller 46 opens valve 366 and after a short period closes valve 374,thus allowing washing fluid to flow into chamber 322 (FIG. 17B).

Next, the controller monitors the temperature of the fluid in thechamber. When this temperature reaches about 58° C., the controllerdisconnects element 304 from the battery and waits for the driver toactivate pump 40 again (FIG. 17C). When the pump is activated again, thepressure is sensed by valve 366 and causes the valve to open. When thevalve opens, controller 46 senses this action and causes valve 374 toopen as well. The result is that hot water flows from chamber 322through outlet 36 to windshield 24 (FIG. 17D). The initial surge isactually a mixture of hot water and steam, which causes any ice on sprayheads 32 to melt and to clear the nozzles of the spray heads. Steam mayalso be generated in the position of FIG. 17A due to some water leftover in chamber 322 from the previous operation.

After pump 40 stops the pressure pulse, valves 366 and 374 stay open,allowing water to flow back from outlet 36 through chamber 322 and outagain through inlet 34 to reservoir (FIG. 17E). When this back-flowstops, as sensed by valve 374, this latter valve closes FIG. 17F).Controller 46 then forces valve 366 to close as well (FIG. 17G). Thus,an amount of fluid is trapped in chamber 322, and element 304 startsheating the fluid When the fluid reaches 58° C., element 304 is turnedoff, and vessel 300 waits for the next operation of pump 40 (FIG. 17H).This operation is sensed (FIG. 17I), as described above, causing thewhole process to repeat again (FIG. 17J).

Controller 46 times the interval between the last back-flow and the nextpressure surge from pump 40. If over a minute is measured, and nopressure is sensed, controller 46 purges chamber 322 by first closingvalves 366 and 374 (FIG. 17K) and activating element 304, to raise thefluid in the chamber to a very high temperature. Then the valves open(FIG. 17L), allowing the fluid to escape as steam. Controller 46 thenpowers down and waits for the next operation. A similar process may beapplied to vessel 150 (shown in FIGS. 9–13B).

It will be appreciated that the preferred embodiments described aboveare cited by way of example, and the fill scope of the invention islimited only by the claims.

1. Apparatus for cleaning a window of a vehicle, comprising: a vessel,having an inlet through which a washing fluid may be received from areservoir and an outlet through which the fluid may be discharged to atleast one spray head for cleaning the window; a heating element forheating the fluid in the vessel; and a bypass through which fluid maybeselectably conveyed from said reservoir to said at least one spray head,said apparatus having a controller configured to automatically conveyfluid through the bypass when cleaning of the window is required whilefluid is not available from the vessel.
 2. Apparatus according to claim1, and further comprising: one or more temperature sensors, whichgenerate signals responsive to an operating temperature of theapparatus; and wherein said controller receives said signals andregulates discharge of the fluid from the vessel responsive thereto. 3.Apparatus according to claim 1 and wherein said controller is operativeto intermittently release quantities of the fluid through the outlet. 4.Apparatus according to claim 3, and further comprising a windshieldwiper which is activated intermittently to clean the window responsiveto the intermittent release of the fluid.
 5. Apparatus according toclaim 3, wherein said controller regulates the intermittent release ofthe fluid according to a given timing sequence.
 6. Apparatus accordingto claim 5, wherein the timing sequence is varied responsive to anambient temperature in the vehicle.
 7. Apparatus according to claim 5,wherein the timing sequence is varied responsive to a temperature of anouter surface of the window.